But these overgrown patches were nothing compared with the jungles unearthed in Journeys into the Outside with Jarvis Cocker (C4). As an art student at St Martin's, Cocker became dismayed by what he saw as the divorce between art and life, and got interested in the notion of "outsider art" - art produced beyond the confines of the art-world by people creating because they needed to, not because they had been taught to. He wrote a dissertation on the subject, which got the second lowest mark in his year.
Last night's programme, the first of three, followed Cocker to France, where there is a tradition of outsider art on a monumental scale. The Rochers Sculptes consist of 300 faces and figures carved out of the rocks on the seashore near St Malo 100 years ago by a retired priest. Buck-toothed, pointy-eared, bulging-eyed homunculi and giant Easter Island heads, struggling out of the rock and now, having been eroded by tourists and the sea, slowly melting back into it. Then on to the house of Robert Vasseur - a single giant mosaic, the garden filled with fountains in order to carry more shards and seashells in bizarre, crude pictures and patterns. Cocker visited Bodhan Litnianski next, a Ukrainian emigre whose garden is crammed with concrete columns encrusted with the debris of modern life - hosepipes, bicycle wheels, TVs, children's boots, and the detached limbs and heads of dolls.
Enumeration falls short of the spectacle. What separated these self-taught artists from the educated collectors in Close Up was a total absence of discrimination, an inability to discard an idea. Enchanted and humbled, Cocker seemed content to bask in the weirdness of these agglomerations of detritus. But you had to wonder what it was like to live next door to one of these unchecked outpourings of personality - like being trapped in perpetual conversation with an egomaniac, I would guess.
You had to wonder, too, what motives lay behind it all. At the home of Raymond Isidore in Chartres, another dizzying catastrophe of mosaic, Cocker learned that Isidore had suffered mental problems. Perhaps primed by that information, he found in the house evidence of a desperation he didn't see elsewhere. But sanity seemed foreign to all the stories of visions, and mysterious compulsions that the artists offered. "Maybe you don't have to be mad to build a large-scale visionary environment," Cocker said, "but it helps." The camera lingered a moment on Chartres cathedral, a large-scale visionary environment if ever there was one.
The unwillingness of the programme to risk an explanation was a flaw, but perhaps it was a necessary price for the enthusiasm Cocker brought to the subject. As a whole, the film was an eloquent argument in favour of weeds - which may not be pretty, but are chock full of life.